Computer graphic techniques have proven to be particularly effective in the generation and manipulation of multistroke characters such as those employed in Chinese writing. It is quite easy, for example, to create on the screen of a cathode ray tube a multistroke character such as that illustrated in FIG. 1 of the drawings. And one of the advantages of computer character generation is that the size of the character can be readily adjusted with simple programs.
In many instances it is desirable to present a character in border, or outline, i.e. hollow, form only. By utilizing a suitable algorithm it is possible to analyze each stroke of the character and produce an image representing the borders only of the stroke. In the case of the multistroke character with overlaying strokes this results in an undesirable, or imperfect, hollow character such as that depicted in FIG. 2. The desired hollow character has the quality illustrated in FIG. 3. Note that no border lines appear within the interior of the character.
Techniques have been developed for processing hollow characters such as shown in FIG. 3. Two such techniques are commonly known as the Differential Method and the Exclusive OR Method. Both of these methods entail the creation first of a solid character and then vertical and horizontal scanning analysis of the solid character to create a border only, hollow, character. These methods are time consuming and require significant quantities of computer memory in order to function.